1. Field of Invention
The present invention relates to an illumination device. More specifically, the present invention relates to a low profile surface illumination device to illuminate an illuminated object such as an image printed on a paper, a liquid crystal display device, and a three-dimensional body.
2. Description of Related Art
Hitherto, a related illumination device disposed on a front side of, for example, a liquid crystal display device described in Japanese Unexamined Patent Application Publication No. 10-50124, Official Gazette is known. In the illumination device described in the Official Gazette, a light source part 404 having a linearly formed organic electroluminescence (organic EL) element 402 is disposed adjacent to an end face portion of a light guide plate 401 to illuminate an illuminated object 403, as shown in FIG. 14.
The light source part of the above-described illumination device consists of a separate component, and is coupled with or adjacently disposed on an end face of a light transmission plate. Thus, there have been problems at least in that the loss in the light transmission can be generated at an interface, the parts having the organic EL element formed thereon and the light transmission plate must be dimensionally affordable, and a spatial loss can be generated. Accordingly, a structure for coupling the light source part with the light guide plate may be necessary.
Further, there have been problems with a prior art illumination device in that a plurality of organic EL elements must be built in one light source, and a fine structure must be machined. Thus, the process is complicated and the yield is difficult to improve.
Accordingly, the object of the present invention is to at least solve these problems and to provide an illumination device high in efficiency and suitable for reduction in size by forming the organic EL elements on the light guide plate or allowing the light to be incident thereon from a plurality of directions of the light guide plate.
An illumination device according to one exemplary embodiment of the present invention is an illumination device which includes a transparent light guide plate and a light source provided adjacent to the above-described light guide plate, and which illuminates an illuminated object by the light emitted from the above-described light guide plate. The above-described light source is an organic electroluminescence element formed on at least one surface of a light emission side main surface and a counter light emission side main surface of the above-described light guide plate. The transmission loss can be reduced by integratedly forming a light guide plate part with a light source part.
In an illumination device according to another exemplary embodiment of the present invention, uneven-shaped portions for light diffusion are provided on the above-described light guide plate in the illumination device described above. The light from the above-described light source transmits in the above-described light guide plate, is diffused in a part of the above-described uneven-shaped portions, and illuminates the above-described illuminated object. The reflected light from the above-described illuminated object transmits in the above-described light guide plate, and is emitted therefrom. The illumination efficiency can be increased by providing the uneven-shaped portions.
In an illumination device according to another exemplary embodiment of the present invention, the illumination device described above further includes a light reflecting part provided on an end face of the above-described light guide plate. The light which is emitted from the end face but does not contribute to the illumination out of the light emitted from the organic EL element can be reduced.
In an illumination device according to another exemplary embodiment of the present invention, the above-described uneven-shaped portion includes a light emission side main surface of the above-described light guide plate, a surface substantially parallel to the light emission side main surface, and a surface substantially perpendicular to the light emission side main surface in the illumination device described above. The light emitted from the light guide plate can be deflected to one side, and illumination can be realized without damaging an image on the illuminated object.
In an illumination device according to another exemplary embodiment of the present invention, the above-described illuminated object is a display device in one of the illumination devices described above, and a front side of its display surface is illuminated. An illumination device of a so-called front light system can be realized thereby.
An illumination device according to another exemplary embodiment of the present invention is an illumination device which includes a transparent light guide plate and a light source provided on the above-described light guide plate, and illuminates an illuminated object by the light emitted from the above-described light guide plate. The above-described light source may include an organic electroluminescence element, and provided on at least one of a plurality of end parts on a main surface of the above-described light guide plate.
In an illumination device according to another exemplary embodiment of the present invention, the above-described light sources different in light emitting color from each other are disposed on at least two end parts out of a plurality of above-described end parts in the illumination device described above. In this constitution, the light sources can be individually manufactured, and the efficiency and the yield can be improved.
In an illumination device according to another exemplary embodiment of the present invention, the main surface of the above-described light guide plate is substantially rectangular, and the above-described light sources of the same light emitting color are respectively disposed on the end parts opposite thereto in the illumination device described above. The uniformity of the light emitting color can be improved by setting the same light emitting color of the organic EL elements opposite to each other.
In an illumination device according to another exemplary embodiment of the present invention, the above-described light sources of three colors different in light emitting color are respectively disposed on a plurality of end parts of both main surfaces of the above-described light guide plate in the illumination device described above. A white light can be easily obtained by mixing the lights in the light guide plate if three light emitting colors of the light sources are red, green and blue.
In an illumination device according to another exemplary embodiment of the present invention, a plurality of light sources different in light emitting color from each other are provided on the above-described end parts in one of the illumination devices described above.
In an illumination device according to another exemplary embodiment of the present invention, a transparent electrode for driving the light source is provided in the vicinity of an end part on which the above-described light source is provided in the main surface of the above-described light guide plate in one of the illumination devices described above. No transparent electrode is provided on a center portion of the light guide plate, and the transmissivity and the reflectance can be improved.
In an illumination device according to another exemplary embodiment of the present invention, the above-described light guide plate further includes uneven-shaped portions for light diffusion provided on at least one of the above-described main surfaces, and a transparent electrode for driving the light source provided so as to cover the above-described uneven-shaped portions in one of the illumination devices described above. The surface resistance of the transparent electrode can be reduced, and the uniform light emission can be realized.
In an illumination device according to another exemplary embodiment of the present invention, the illumination device described above further includes an auxiliary electrode which is provided in an area other than the area having the above-described uneven-shaped portions, and electrically connected to the above-described transparent electrode to supply the power to the transparent electrode. The organic EL element can be driven more stably by providing the auxiliary electrode on a part not influential on the illumination effect.
In an illumination device according to another exemplary embodiment of the present invention, the above-described illuminated object is a display device and a reverse side of its display surface is illuminated in one of the illumination devices described above. An illumination device of the so-called back light system can be realized thereby.